This invention relates to a network management server for managing a network and a recovery method therefor.
Background arts of this technical field include JP 2013-46322 A, JP 2013-85061 A, and WO 2010/018755 A1. In the technology disclosed in JP 2013-46322 A, a network management system includes a plane management table for managing a transmission plane defined as a set of transmission paths within a transmission network. Further, the plane management table sets and manages not only a transmission plane (active plane) applied at a normal time but also at least one transmission plane (standby plane) applicable when a failure occurs in the transmission network. When a failure occurs in the transmission network, the network management system changes an applied plane to an appropriate transmission plane.
In the technology disclosed in JP 2013-85061 A, respective communication apparatus are classified into a plurality of areas, each of which includes an edge node through which an active path first passes and an edge node through which the active path last passes. The network management apparatus holds failure information including a value indicating whether or not a failure has occurred in each area, and also holds alternative path information including a value indicating a plurality of edge nodes, a value indicating an alternative area of each area, and a priority assigned to each alternative area. When it is determined that the failure has occurred in a first area based on the failure information, the network management apparatus identifies the alternative area of the first area based on the alternative path information. When it is determined that the failure has not occurred in the alternative area of the first area, the network management apparatus determines the alternative area of the first area as a second area through which the active path passes, determines two edges nodes included in the second area based on the alternative path information, and detects each communication apparatus through which the active path between the two edge nodes passes.
In the technology disclosed in WO 2010/018755 A1, a path generation module generates in advance standby path information to be used when a failure occurs based on predicted topology information and predicted resource information, which are changed in accordance with a predicted failure site. The path generation module stores the generated standby path information in a data storage unit. A path information notification module of a transport control server (TCS) (S-1) notifies a node N of generated normal path information. A failure information acquisition module of the TCS (S-1) detects an occurrence of a failure. When the failure information acquisition module detects the occurrence of a failure, the path information notification module notifies the node N of the standby path information stored in the data storage unit.
However, in the technology disclosed in JP 2013-46322 A, when a failure has occurred in a specific set path, it is determined whether or not the path is available, for all the paths that pass through a plurality of relay points in the standby plane, and the standby plane affected least by the failure is selected based on the priorities of the respective paths. Therefore, it is necessary to execute a considerable amount of processing from the detection of the failure in the set path until the determination of the standby plane for recovery. Accordingly, it is more difficult to apply the technology to a communication system having a larger scale.
In the technology disclosed in JP 2013-85061 A, when a failure is detected in the area to which the communication apparatus belongs, already-set path settings for the paths passing through the area that has caused the failure are abolished one by one in order, and then path settings as bypasses are enabled. Therefore, it is necessary to execute a considerable amount of processing until all the already-set paths are recovered, and because the bypasses are determined and set one by one, the path settings optimal as a whole cannot be executed. Accordingly, it is more difficult to apply the technology to a communication system having a larger scale.
In the technology disclosed in WO 2010/018755 A1, the standby path information to be used when a failure occurs is calculated in advance, and each node is notified of different standby path information or a different ID indicating the path information. Therefore, when a large number of nodes exist, it is necessary to notify each node of an enormous number of different pieces of path information or necessary to establish coupling to the large number of nodes to be notified and notify the nodes of the large number of different IDs, which imposes a heavy load on the side that notifies of the path information or necessitates much time for the notification. Accordingly, it is more difficult to realize quick recovery for a communication system having a larger scale.